Search PubMed⌕ Search

Biomedical subjects

A Pines

Publications and source records attributed to A Pines.

At least 55 records · Page 3Linked to original sources
PubMed1999

Gas flow MRI using circulating laser-polarized 129Xe.

We describe an experimental approach that combines multidimensional NMR experiments with a steadily renewed source of laser-polarized 129Xe. Using a continuous flow system to circulate the gas mixture, gas phase NMR signals of laser-polarized 129Xe can be observed with an enhancement of three to four orders of magnitude compared to the equilibrium 129Xe NMR signal. Due to the fact that the gas flow recovers the nonequilibrium 129Xe nuclear spin polarization in 0.2 to 4 s, signal accumulation on the time scale of seconds is feasible, allowing previously inaccessible phase cycling and signal manipulation. Several possible applications of MRI of laser-polarized 129Xe under continuous flow conditions are presented here. The spin density images of capillary tubes demonstrate the feasibility of imaging under continuous flow. Dynamic displacement profiles, measured by a pulsed gradient spin echo experiment, show entry flow properties of the gas passing through a constriction under laminar flow conditions. Further, dynamic displacement profiles of 129Xe, flowing through polyurethane foams with different densities and pore sizes, are presented.

Equipment Design↗
PubMed1999

The effect of various hormonal preparations and calcium supplementation on bone mass in early menopause. Is there a predictive value for the initial bone density and body weight?

OBJECTIVES: To compare the effect of various oestrogen and oestrogen/progestin preparations on bone density over a 2-year follow-up period in early postmenopausal women. SETTING: A retrospective study on 315 women followed in a menopause clinic. DESIGN: Antero-posterior lumbar spine bone densitometry was performed at baseline and between 18 and 24 months (mean 22 months) after initiation of hormone therapy. Participants were divided into six groups: women taking conjugated equine oestrogen (CEE) (n = 30); CEE plus sequential monthly medroxyprogesterone acetate (MPA) (n = 52); CEE plus sequential bimonthly MPA (n = 51); oral estradiol plus sequential monthly norethisterone acetate (n = 52); transdermal estradiol plus sequential monthly MPA (n = 30). A control group (n = 100) was composed of nonusers of hormones. RESULTS: Hormone users, as a whole (n = 215), increased their bone mineral density (BMD) by 2.9% (4.8) as compared to the controls who lost 3.5% (3.4; P < 0. 001). There were similar gains in BMD amongst the five study groups. Calcium supplementation was associated with better results in all women: users of hormones and calcium had a gain in BMD of 4.5% (4.8) compared to only 1.5% (4.5) in those on hormones but without calcium (P < 0.001); amongst the controls, women using calcium lost 1.4% (2. 4), whilst nonusers of calcium lost 3.7% (2.4; P < 0.001). A dose-response curve was found between basal BMD and the effect of hormone therapy: women with osteoporosis (T-score <75%) demonstrated the largest increase in BMD - 6.3% (4.6), osteopenia (T-score 75-85%) was associated with a gain of 3.2% (5.6), low-borderline values (T-score 86-100%) gave a modest increase of 1.3% (4.3), and those with more than average BMD values (T-score >100%) actually lost bone despite hormone treatment [-2.1% (4.1)]. CONCLUSIONS: All hormone regimens had a similar bone conserving effect. Basal BMD value may serve as a predictor for the success of treatment. Calcium supplementation should be recommended in all postmenopausal women.

Body Weight↗
PubMed1999

Short- and long-term follow-up after coronary bypass grafting for single-vessel coronary artery disease.

Short-term outcome and 10-year clinical outcome were reviewed in 114 consecutive patients after coronary artery bypass grafting (CABG) for single-vessel coronary artery disease (CAD). Gated equilibrium radionuclide cineangiography was performed soon after CABG in all cases, and revealed very good early graft patency rates. There was no perioperative mortality, and very low morbidity. During follow-up there were seven late deaths, two from cardiac disease and five from non-cardiac causes. Cumulative survival at 10 years was 93%. Cumulative freedom from additional cardiac invasive procedures was 96%, 93% and 80% at 1, 5, and 10 years, respectively, and cumulative freedom from angina was 93%, 80% and 73%. Conventional single-vessel CABG thus can be safely performed, with minimal postoperative morbidity and no mortality, providing good long-term relief of angina and circumventing need for additional invasive procedures.

Adult↗
PubMed1999

Workers' right-to-know legislation: does it work?

Workers' right-to-know (WRTK) laws and regulations were established to empower workers to protect their health by providing them with information about the hazards to which they are exposed while at work. The present study was conducted to examine the implementation of WRTK regulations in Israel. We interviewed 552 workers and 33 safety officers from a random sample employed at 50 industrial plants. The workers' questionnaire included items on awareness and self-management of workplace hazards, and the safety officers answered questions about job experience and hazards communications to workers. In 36% of cases workers and their safety officers disagreed about the existence of hazards in the workplace (p < 0.001). Most (78%) of the workers' knowledge about work hazards was based on informal sources, i.e., not those stipulated by the regulations. There were also discrepancies between worker and safety officer reports regarding the provision of safety training upon employment (p < 0.001), recent instructions about special risks and distribution of relevant printed material. We found that more than 5% of workers were unable to read the language in which the hazards material was written and 22% had levels of education below that required to comprehend the technical terms used. There are serious problems in the implementation of WRTK regulations in Israel. We recommend that employers be made aware of the importance of these laws and of their proactive duty to comply with them and that the material distributed to workers be written in simpler terms and/or explained orally in a language they understand. These findings have important implications for all countries with similar legislation and should form the basis for further and more comprehensive studies world-wide.

Adolescent↗
PubMed1999

Long-term follow-up after coronary artery bypass grafting reoperation.

BACKGROUND: Coronary artery bypass grafting (CABG) reoperation is being performed with increasing frequency. OBJECTIVE: To determine the clinical outcome and the long-term results of a second CABG. SETTING: An 1100-bed urban university-affiliated hospital. DESIGN: Retrieval of data on selected parameters from medical records before surgery and prospective follow-up afterwards. PATIENTS AND METHODS: We studied the outcomes of 498 consecutive patients who underwent CABG reoperation in our institution from January 1978 to December 1989 and who were followed postoperatively. Their perioperative mortality, morbidity, and long-term follow-up results were re-evaluated. The end points of the study were December 1997, 15 years of follow-up, or the patient's death. RESULTS: The perioperative mortality rate was 3%. The cumulative survival rates were 90.1%, 74%, and 63.4% at the 5-year, 10-year, and 15-year follow-ups, respectively. The cardiac event-free survival rates were 91.5%, 83.4%, and 67.8% at the 5-year, 10-year, and 15-year follow-ups, respectively. The risk factors adversely affecting long-term survival were advanced age, hypertension, and a low left ventricular ejection fraction (LVEF). CONCLUSIONS: The long-term results of cumulative survival and cardiac event-free survival in patients who underwent CABG reoperation are good. Although this reoperation is safe overall, advanced age, hypertension, and a decreased LVEF significantly increase the surgical risk.

Adult↗
PubMed1999

L-thyroxine prevents the bone-conserving effect of HRT in postmenopausal women with subclinical hypothyroidism.

Hypothyroidism, which is a common disorder among postmenopausal women, may be associated with higher than average bone mineral content. Contrarily, treatment with L-thyroxine may cause a significant bone loss. The aim of our study was to evaluate the effects of hormone-replacement therapy (HRT) on bone density in women with subclinical hypothyroidism treated with L-thyroxine. A total of 73 postmenopausal women with thyroid-stimulating hormone (TSH) levels > 5 mU/l and normal free thyroxine values, who never used HRT or L-thyroxine, were divided into three groups according to the treatment given during a 3-year follow-up period: 34 women received only HRT; 20 women received HRT and L-thyroxine, and the remaining 19 women received neither medications. A euthyroid control group included 41 postmenopausal women with TSH levels between 0.5 and 1.5 mU/l, who were using HRT since the initial visit. Lumbar spine bone density measurements were performed at baseline and study termination. Taken as a whole, the hypothyroid women had a non-significant higher baseline bone mineral density (BMD) as compared to the euthyroid controls (1.068 +/- 0.19 g/cm2 vs. 1.024 +/- 0.15). After 3 years, both the euthyroid and hypothyroid women on HRT only had an increase in BMD (0.032 +/- 0.04 g/cm2 and 0.028 +/- 0.05 g/cm2, respectively; p < 0.001 for both, compared to baseline). Hypothyroid women using no medication had a decrease of 0.034 +/- 0.07 g/cm2 in BMD, and those receiving both HRT and L-thyroxine lost the most: 0.04 +/- 0.08 g/cm2 (p < 0.05 for both, compared to baseline). The addition of L-thyroxine thus prevented the beneficial effect of HRT on BMD. Thyroid hormone replacement is recommended only when overt symptoms of hormone deficiency occur. In such cases, a single bone-conserving treatment with HRT may not suffice.

Adult↗
PubMed1999

Lack of effects of transdermal estradiol on diastolic function: a randomized placebo-controlled double-blind short-term trial.

OBJECTIVE: Limited information is available on the effects of transdermal estradiol on diastole. The present study was a randomized double-blind placebo-controlled trial designed to investigate the short-term effects of transdermal estradiol on left ventricular diastolic function in postmenopausal women. METHODS: The study included 45 women aged 50.8 +/- 3.6 years (25 randomized to the study group and 20 to placebo), who underwent Doppler echocardiography and determination of the plasma estradiol level after 4 and 8 weeks of transdermal estradiol administration in a dose of 50 micrograms per 24 h. RESULTS: There were no modifications in heart rate. Systolic blood pressure dropped in the study patients after 8 weeks (p < 0.03); diastolic blood pressure remained unchanged. Estradiol levels were 67 +/- 36 pg/ml at 4 weeks and 70 +/- 49 pg/ml at 8 weeks in the study group. Basal values of peak early and peak atrial velocities, acceleration time and rate, deceleration time and rate, early/atrial velocity ratio and pressure half-time were not significantly different between the estradiol and placebo groups. Doppler values remained unchanged after both 4 and 8 weeks in women receiving estradiol. Women with relatively high serum 17 beta-estradiol levels (> 100 pg/ml) at 4 or 8 weeks of treatment did not present more pronounced changes in the Doppler-derived parameters compared with patients with low hormone levels. CONCLUSION: The results showed a lack of short-term effects of transdermal estradiol on left ventricular diastolic function in postmenopausal women, irrespective of serum estradiol levels.

Administration, Cutaneous↗
PubMed1998

Surface NMR Using Laser-Polarized 129Xe under Magic Angle Spinning Conditions

NMR signals of surface nuclei of solids may be enhanced by the transfer of spin polarization from laser-polarized noble gases. Until now such experiments have not been feasible under conditions of magic angle spinning. In the present contribution it is shown that laser-polarized 129Xe can be inserted into a spinning rotor under continuous-flow conditions using helium as a carrier gas. Effective adsorption of xenon on the sample occurs at temperatures of about 163-173 K making possible the observation of a spin polarization induced nuclear Overhauser effect (SPINOE) from the laser-polarized 129Xe to surface 1H nuclei of SiO2 (AEROSIL300). This technique opens the way to selectively enhanced high-resolution multinuclear surface NMR experiments. Copyright 1998 Academic Press. Copyright 1998 Academic Press

Journal Article↗
PubMed1998

Surface selective 1H/29Si CP NMR by NOE enhancement from laser polarized xenon

The surface proton spin polarization created by the spin-polarization-induced nuclear Overhauser effect from optically polarized xenon can be transferred in a subsequent step by solid-state cross polarization to another nuclear spin species such as 29Si. The technique exploits the dipolar interactions of xenon nuclear spins with high gamma nuclei such as 1H, and is experimentally simpler than direct polarization transfer from 129Xe to heteronuclei such as 13C and 29Si. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

In situ NMR analysis of fluids contained in sedimentary rock

Limitations of resolution and absorption in standard chemical spectroscopic techniques have made it difficult to study fluids in sedimentary rocks. In this paper, we show that a chemical characterization of pore fluids may be obtained in situ by magic angle spinning (MAS) nuclear magnetic resonance (NMR), which is normally used for solid samples. 1H MAS-NMR spectra of water and crude oil in Berea sandstone show sufficient chemical shift resolution for a straightforward determination of the oil/water ratio. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Effect of estradiol on rat ileum.

1. Sex hormones may influence gastrointestinal motility and thus may be responsible for symptoms that are common during pregnancy or hormone replacement therapy. The purpose of this study was to evaluate the effect of estradiol on the gut. 2. Segments of rat ileum (n=9) were suspended in an organ bath and exposed to increasing concentrations of carbachol, in the presence or absence of 17beta-estradiol. 17beta-estradiol markedly reduced the force developed by the ileum in response to carbachol. 3. These results suggest that estradiol reduces gastrointestinal motility.

Animals↗
PubMed1998

Imaging of laser-polarized solid xenon.

The enhanced spin polarization produced by optical pumping of gaseous rubidium/xenon samples has made possible a number of recent experiments in nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI). Here we report MRI of laser-polarized xenon in the solid phase at low temperature. Due to the high xenon density in the solid phase and the enhanced spin polarization, it is possible to achieve high intensity and spatial resolution of the image. Signals were observed from xenon films solidified onto the glass container walls and not from an enclosed chili pepper.

Lasers↗
PubMed1998

Exercise-induced aortic flow parameters in early postmenopausal women and middle-aged men.

OBJECTIVE: Exercise Doppler echocardiography has been recognised as an accurate method for the assessment of left ventricular function in patients with coronary artery disease. Gender differences in aortic flow parameters during exercise have not been well established. The aims of this study were to compare basal ejection Doppler indexes in healthy early postmenopausal women with those of men, and to assess the effects of both isometric and dynamic exercises on these parameters. DESIGN: Intergroup comparison between early postmenopausal women and middle-aged men. SUBJECTS: Fifteen healthy women with a mean age of 55 (SD 5) years and 15 healthy men aged 52 (SD 4) were evaluated. SETTING: Women were recruited from a menopause clinic and men from a primary cardiovascular prevention program at a cardiac rehabilitation institute. INTERVENTIONS: Isometric exercise was performed with a 2-hand bar dynamometer, and dynamic exercise with a supine ergometer. Echo Doppler examination was performed at rest and at peak isometric and dynamic exercise with a pulsed Doppler transducer. RESULTS: Both types of exercise resulted in higher values of hemodynamic parameters in the women, with most figures reaching statistical significance. Most aortic flow parameters during rest and exercise were also significantly higher in the women. CONCLUSIONS: The unexpected higher values in hemodynamic and aortic flow parameters in early postmenopausal women as compared with middle aged men may shed light on a peculiar aspect of gender differences in cardiovascular function, perhaps specific to this age group and related to menopausal transition.

Aorta↗
PubMed1998

Hormone replacement and simvastatin in the therapy of hypercholesterolemic postmenopausal women.

OBJECTIVES: To prospectively investigate the effect of cholesterol lowering diet, hormone replacement therapy and simvastatin on plasma lipid levels using a 3-month stepwise protocol. METHODS: Participants were postmenopausal women under the age of 60 with hypercholesterolemia (plasma total cholesterol > 240 mg/dl). The study started with 3 months of Step-One diet (phase I) followed by 3 months of diet and hormone replacement therapy (0.625 mg conjugated estrogens daily combined with 5 mg medroxyprogesterone acetate at days 13-25 of each cycle) (phase II). In women whose total cholesterol remained above 240 mg/dl or LDL-cholesterol above 160 mg/dl by the end of phase II, simvastatin at 10 mg daily was added (phase III). Plasma cholesterol levels as well as safety measurements were closely monitored. RESULTS: Sixteen (21%) of 75 patients who entered the study had satisfactory cholesterol levels by the end of 6 months. Another 25 patients (33%) dropped out of the study for various reasons by that time. In the 34 patients who started simvastatin, plasma total cholesterol levels did not significantly change during phase I and II, however, LDL-cholesterol significantly decreased (204 +/- 31 to 187 +/- 26 mg/dl, p = 0.04) and HDL increased (53 +/- 12 to 62 +/- 16 mg/dl, p = 0.04). A dramatic decrease occurred in both total and LDL-cholesterol levels after one month of phase III (281 +/- 26 to 213 +/- 30 mg/dl 187 +/- 26 to 122 +/- 30 mg/dl respectively, p < 0.0001), with no further changes during the rest of the study period. No significant changes occurred in HDL-cholesterol and triglyceride plasma levels at this phase. Adverse effects were few and minor throughout the study. CONCLUSIONS: Some of the hypercholesterolemic postmenopausal women will benefit from hormone replacement therapy as a single cholesterol lowering treatment in addition to diet (21% in our series). Nevertheless, combination therapy of estrogens and low dose simvastatin proved to be extremely effective in lowering cholesterol levels with no significant side effects. Such therapeutic regimen may also have a synergistic anti-atherogenic effect.

Anticholesteremic Agents↗